Derek Mackay has said he will make "balanced considerations" on tax and spending when he reveals his draft Budget plans for 2019-20.

Scotland's finance secretary will lay out his proposals before MSPs later on Wednesday, although Holyrood won't vote on them until mid-February next year.

Between what we get in the chamber today and that final vote, all kinds of jockeying and negotiation could take place.

As a minority government, the SNP administration depends on support for its Bills from other parties.

When it comes to the annual Scottish Budget, that backing has, since the 2016 election, typically come from the Scottish Greens.

What are the key things to look out for when the finance secretary lays out his plans?

Will you pay less or more in income tax next year? It will depend on what you earn.

Last year, Scottish income tax diverged from the rest of the UK in a big way, with the addition of two new tax bands.

Derek Mackay brought in a 19% rate on income between £11,851 and £13,850; 20% for those earning between £13,851 and £24,000; and 21% if you're on a salary of £24,001 up to £44,273.

Rates also went up to 41% for those on £43,430 to £150,000, and to 46% for people earning more than £150,000 - 1% higher than for the rest of the UK.

But the 19% rate meant that only those earning £33,000 or above actually had to pay more income tax than they did previously.

This year, the finance secretary faces pressure to match the tax relief handed out by Chancellor Philip Hammond in the UK's Autumn Budget.

After raising the personal allowance to £12,500 - the amount you can earn before paying any tax, which also applies to Scottish taxpayers - he also raised the 20p threshold to those earning up to £50,000.

This means if income tax thresholds rise in line only with inflation, people earning between £44,472 and £50,000 could take a yearly hit to their paypackets of around £300 compared to their English counterparts.

With the Scottish Parliament receiving new welfare powers, and the creation of a Scottish social security agency, Mackay has some flexibility on this.

He is likely to do as in years past and pledge a sum to mitigate the effects of controversial UK Government welfare reforms such as Universal Credit.

The government has also previously vowed to bring in an income supplement by 2022.

But some groups, like the Child Poverty Action Group and the Church of Scotland, want to see more sooner - like a £5 a week top-up to child benefit payments.

Another policy Mackay could seek to end or mitigate would be the divisive two-child cap on tax credits.

Associated with that is the so-called "rape clause" - an exemption to the two-child cap which requires claimants to prove a child was conceived through rape or during an abusive relationship to qualify.

Nicola Sturgeon has called the policy "abhorrent" - but stopping it costs money.

Scottish Labour believes it would cost £69m for the finance secretary to effectively abolish both the two-child cap and the "rape clause".

The Tories and the Lib Dems say they won't support the Budget unless the Scottish Government rules out a second independence referendum - and you can forget that.

Labour has a series of demands, including "proper funding for councils", a £5 per week increase to child benefit, an end to the two-child cap and "rape clause" and a freeze on ScotRail fares in the New Year.

That's not even all of them - and Mackay isn't likely to satisfy Richard Leonard's party on every one.

It seems likely the SNP will once more need to compromise with the Greens, which last year brought a boost to council funding and more public sector pay rises.

This year, Scottish Greens' co-convener Patrick Harvie says the Scottish Government must act on its long-standing pledge to reform local taxation.

He is demanding "substantial progress" on replacing council tax with something fairer - or Mackay could lose Green support.

Derek Mackay will present his third Budget to the Scottish Parliament today, but there is no vote until the New Year.

That is just as well because he hasn't got a Budget partner yet to get see the minority government through.

The Greens are his most likely allies - they've done the deal in the past securing extra funding for councils and income tax reform. This time they want more of the same and the promise of a review of local authority funding leading to council tax being replaced and they want council to get the powers to have a Tourist Tax.

The Conservatives say he has an extra £950m from the Chancellor's UK Budget and are urging the him to go blue instead of green and equalise income tax with the rest of the UK.

That is just not going to happen.

Last year Derek Mackay used the new devolved income tax powers to create a new starter rate of income tax below the UK basic rate. Scotland also has an intermediate rate for middle earners and higher earners do pay a bit more than down south.

I expect that to continue - Scotland will keep five tax bands instead of the rest of the UK's three. Workers in Scotland earning less than the average income of around £26,000 will continue to pay slightly less than in the rest of the UK, and those earning more will pay a little more, while those earning more than £50,000 will pay a bit more again.

That deal raises an extra £340m a year for public services and Derek Mackay will argue that people paying a bit more are getting a good deal from free university tuition, free prescriptions, care for the elderly and increasingly free child care.

There will be more cash for health, early years and investment in town centres and a lot of opposition focus on funding for councils, but most of us will also want to know what the Budget means for the tax we pay and the services we use.

We'll tell you tomorrow right here and on the STV News at Six.